END-TIDAL PARTIAL-PRESSURE OF CARBON-DIOXIDE AS A NONINVASIVE INDICATOR OF SYSTEMIC OXYGEN-SUPPLY DEPENDENCY DURING HEMORRHAGIC-SHOCK AND RESUSCITATION

When oxygen delivery (DO2) critically decreases, oxygen consumption (V O2) becomes supply dependent. We examined whether end-tidal PCO2 (PetC O(2)) would identify supply dependency during shock. Five dogs (Group I) underwent progressive hemorrhage to decrease DO2 until they could n o longer maintain a stable blood pressure, Five additional animals (Gr oup II) were bled until VO2 decreased to 70% of baseline, followed by resuscitation, The PetCO(2) versus time inflection point was compared with the DO2 at onset of supply dependency (Do(2)crit). Do(2)crit for Groups I and II were 6.9 +/- .4 and 8.1 +/- 1.3, respectively (p = NS) , and not statistically different from the DO2 values at which PetCO(2 ) decreased (6.6 +/- .7 and 6.3 +/- .7 mL/kg per min, respectively). A t constant minute volume, PetCO(2) effectively indicated the onset of supply dependency and rapidly increased during resuscitation, parallel ing the changes in VO2 in this model of hemorrhagic shock.